Milling grooves in Campagnolo NR seatposts was quite a popular thing to do. Often the grooves were painted to match the frame. I have a 1960's Condor with original NR groupset with this modification and I have seen other examples. The chances are that your seatpost has had this modification from new.
In a message dated 15/11/00 01:04:50 GMT Standard Time, firstname.lastname@example.org writes:
<< Can someone advise what I have...
Campagnolo seatpost off a bike equipped with a combo of Campagnolo NR and SR components. This seatpost is identical to a 2 bolt NR post except it has six slots machined into it. The slots are of uniform depth from end to end (ie. no taper to the slot at each) and appear to be machined in, not originally cast in. They are only about 1mm in depth. Don't SR posts have slots with tapers in them at the ends and aren't the slots deeper? Is this a special NR, special SR or just a normal SR?
Eric "Feel as though I should know this" Elman >>